This invention relates generally to methods and apparatus for the high-temperature, high-pressure bonding of a plurality of nested tubular components to form a unitary assembly thereof. More particularly, it relates to a tool which under such conditions produces a continuous, uniform bond between confronting surfaces of such components. The invention also relates to a method for bonding such components.
A well-known technique for the production of certain radioisotopes and fission products comprises subjecting a cooled metallic target to irradiation from a nuclear reactor or a particle accelerator. Often, the target is in the form of a flat sandwich comprising a thin metal foil diffusion-bonded to a relatively thick substrate composed of a dissimilar metal. The substrate provides physical support for the foil and conducts irradiation-induced heat from the foil to a suitable cooling medium, such as circulated water or gaseous helium.
In some target applications, a tubular target is preferred. For example, in the production of certain fission products, the target comprises a thin, tubular uranium foil nested within and bonded to a thicker tubular aluminum-alloy substrate. Hitherto, the preferred technique for forming tubular targets has comprised superimposing flat sheets of the foil and substrate materials, rolling the superimposed sheets to form a tube having two abutting edges, and welding these edges to form a leaktight seam. Unfortunately, that method is relatively complex and does not provide as uniform a target as is desired. Furthermore, complete dissolution of both the target and the substrate is necessary for satisfactory recovery of the desired radioisotopes or fission products. Tubular targets also have been formed by isostatic processing, but that method requires large equipment and very high pressures.